Learn French: Il n'y a pas de charbon ici, mais ils auront creusé un trou. - There is no coal here, but they will have dug a hole.

It combines the futur simple of the helping verb with a past participle. Here, the helping verb is avoir conjugated for ils (auront), followed by the past participle of creuser (creusé). It translates literally to "will have dug."

Why is the helping verb avoir (auront) instead of être (seront)?

In all compound tenses (like the passé composé or this futur antérieur), the verb creuser (to dig) takes avoir. You only use être for reflexive verbs (like se laver) and specific verbs of movement or state change (like aller, venir, mourir).

Why does the sentence say pas de charbon instead of pas du charbon?

This is a strict rule of French negation. In an affirmative sentence, "some coal" is du charbon. But when a sentence becomes negative, indefinite and partitive articles (un, une, des, du, de la) change to a simple de or d'.

Should creusé have an "s" at the end to match the plural subject ils?

No, because the helping verb is avoir. When a compound tense uses avoir, the past participle never agrees with the subject. It only agrees with a direct object if it is placed before the verb, which doesn't happen here since un trou comes after the verb.